Process of making leucogallocyanins.



UNITED STATES PATENT oEEIoE.

CHARLES DE LA HARPE, OF BASEL, SWITZERLAND, ASSlGNOR TO THE FIRM OF DYEWORKS,

FORMERLY L. DURAND, HUGUENIN & 00., OF BASEL, SWITZERLAND PROCESS OFMAKING LEUCOGALLOGYANINS.

Specification of Letters Patent.

Patented Aug. 20, 1907.

Application filed May 16,1907. Serial No. 374,068.

To all whom it may concern:

Be it known that 1, CHARLES DE LA HARPE, chemist,

a citizen of the Swiss Republic, and a resident of Basel,

Switzerland, have invented a Process for the Manufacture of theLeucogallocyanin Corresponding to the Pyrogallol, of which the followingis a full and exact specification.

I have found that the leuco compound of the gallocyanin derived fromnitrosodimethylanilin and gallic acid can be converted into theleucogallocyanin corresponding to the pyrogallol, by heating the saidleuco compound, in the form of salts (hydrochlorate, sulfate etc.) or asbase, with water at a temperature of about 100 centigrade. in thepresence or not of a substance containing an alkali oxid, as forinstance sodium ace tate, sodium sulfate, or caustic soda lye, underthese circumstances carbonic acid being split off from the ordinaryleucogallocyanin. This leucogallocyanin corresponding to pyrogallol iseasily oxidized to the corresponding pyrogallol-gallocyanin, as a baseor asan alkali salt, by the oxygen of the air, or as salt(hydrochlorate, sulfate and the like) by the oxidation of the solutionof the salt by means of an oxidizing agent, such as a bichromate,persulfate and the like. The thus obtained oxidized product of theleucogallocyanin correspondingto the pyrogallol is insoluble in sodiumcarbonate, but is soluble in concentrated hydrochloric acid with a bluecoloration.

The following are examples showing how this invention may be carriedout.

Example I. 400 liters of water and 30 kilograms of the hydrochlorate ofleucogallocyanin obtained by means of the gallocyanin derived fromgallic acid and nitrosodimethylanilin, in accordance with the process ofthe first claim of the-United States Letters Patent No. (329666 datedJuly 25, 1899 or of the process of the English Letters Patent 7835 datedApril 12, 1905, are heated in a vat, while being stirred, to the boilingpoint, this temperature being maintained until the transformation iseffected, that is until the solution of the reaction product inhydrochloric acid becomes blue on addition of a little manganese dioxid.The mass is then allowed to cool and the leuco-gallocyanin correspondingto the pyrogallol is salted out.

Example II. Proceed as in example I but in an autoclave instead of anopen vat and add to the mass to be treated 13 kilograms of caustic sodalye of 38 Baum or 10 kilograms of crystallized sodium acetate. Theautoclave is then closed and heated to 100 Centigrade, until thereaction is completed, that is until the pressure no longer raises.Thirteen kilograms of hydrochloric acid of 21 Be. are then added to thereaction mass, which is then allowed to cool and the coloring matter issalted out.

Example III. Proceed as in example I, but add further kilograms ofsodium sulfate. After heating the coloring matter is salted out.

The preparation of the leucogallocyanin according to the specifiedLetters Patent No. 629666 and its transformation into theleucogallocyanin corresponding to the pyrogallol can also be combined ina single operation, that is to say be effected in direct succession.

\Vhat I claim is:

1. The process for the manufacture of a leucogallocyanin correspondingto pyrogallol by heating the ordinary leucogallocyanin, corresponding tothe gallocyanin derived from nitrosodimethylanilin and gallic acid, withwater to about 100 Centigrade.

2. The described process for the manufacture of a leucog'allocyanincorresponding to pyrogallol by heating the ordinary leucogallocyanincorresponding to the gallocyanin derived from nitrosodimethylanilin andgallic acid, with water in the presence of a substance containing analkali oxid.

In witness whereof I have hereunto signed my name this 6 day 01 May1907, in the presence of two subscribing witnesses.

CHARLES DE LA HARPE.

Witnesses GEonGEs CHAIINS, AMAND RI'LTER.

